As a conventional liquid-surface detection device, for example, there is the one disclosed in Patent Literature 1. This liquid-surface detection device was a liquid-surface detection device made of: a float arm provided with a float floating on the liquid surface; an arm holder to hold the float arm and moves concurrently with turning of the float arm; and a frame to turnably support the arm holder, in which a bearing part made of a through hole is provided at the frame, a shaft part to be inserted into the bearing part is provided at the arm holder, an elastically deformable engagingly locking piece provided with an engagingly locking claw is provided at the shaft part, the shaft part is inserted into the bearing part and then is engagingly locked with an engaging part of the bearing part by the engagingly locking claw, and the arm holder is turnably supported at the frame.